Generally, in an electrophotography image forming apparatus such as a copier, a printer, a facsimile or the like, a roller which is provided with electrical conductivity such as a transfer roller, a developing roller, a toner supplying roller, an electrifying roller, a cleaning roller, an intermediate transfer roller, a belt driving roller or the like is employed for each process of the image forming apparatuses.
As such a conductive roller, an electrifying roller or the like has been known which is formed by providing an electrically conductive shaft made of metal or polymer with an elastic layer made of foamed or non-foamed rubber, and providing thereon one or more skin layers. Particularly, in order for an organic photoreceptor to be electrically charged uniformly, the elastic layer of an electrifying roller requires suitable low hardness and low permanent compression set for maintaining the contact surface with a photoreceptor uniform. As a result, conventionally, rubber, elastomer, foam urethane or the like is employed for the material of elastic layers (Patent Documents 1 to 3). Conventionally, for an electrifying roller, an electrically conductive material such as carbon black or ionic electrically conductive material is used for securing a required resistance.
On the other hand, an ultraviolet curing resin is known to be employed as the elastic roller of the electrically conductive roller, and also in the variety of electrically conductive rollers manufactured by using an ultraviolet curing resin, an ionic electrically conductive material is used.
However, ionic electrically conductive materials are highly dependent on the volume specific resistivity, and when a large amount ionic electrically conductive material is used, bleeding occurs.
Accordingly, the use of an electrically conductive material with small environmental variation is considered, and in the Patent Document 4, disclosed is an electrically conductive roller whose elastic layer is composed of an ultraviolet curing resin in which materials for the elastic layer comprising a urethane acrylate oligomer, photopolymerization initiator and lithium salt are cured by ultraviolet irradiation.